noun
long-period comet
Technical term in astronomy for a comet with an orbital period longer than 200 years.
長周期彗星は、太陽系の遠くからやって来る。
Long-period comets come from the far reaches of the solar system.
Refers to a short-period comet with an orbital period of less than 200 years, in contrast to 長周期彗星.
Compound of 長 (long) + 周期 (period) + 彗星 (comet).